[#728] Add ckan.tracking_enabled to app_globals

The ckan.tracking_enabled ini file setting was being ignored, so page
view tracking wasn't working. Adding ckan.tracking_enabled to
app_globals makes the setting work again.

Fixes #728
[#729] Handle languages in URLs when updating page view tracking summary

Page view tracking was failing when a language was selected:

1. Put `ckan.tracking_enabled = true` in your ini file
2. Run CKAN, visit a page with a language e.g. `/en/dataset/annakarenina`
3. Run `paster tracking update`. If you look in your db, in the
   `tracking_summary` table there'll be a row with `package_id`
   `~~not~found~~`.
4. Run `paster tracking export tracking.csv`, the exported CSV file will
   say 0 views.

If you visit the page without the language in the URL e.g.
`/dataset/annakarenina` then run the export command again, the view does
get counted.

This commit fixes the SQL used by the `paster tracking update/export`
command to handle URLs with or without languages at the start.

Fixes #729
[#541] Add docs for page view tracking feature

Add documentation for the page view tracking feature. There are still
some details to document, including how to show number of page views on
the pages themselves (eg. dataset views next to datasets) and how to
show "popular" labels next to popular datasets. It's also possible to
get a list of the N most popular datasets, for example for the front
page, perhaps this should be documented too.
[#541] Add popularity-sorting screenshot

Should have been added in commit 3eeeef2 but I forgot.
[#730] Only show 'Popular' sort option if tracking enabled

Sorting datasets by popularity only works if page view tracking is
enabled, so don't show the 'Popular' option in the 'Order by:' dropdown
if tracking isn't enabled.
[#714] Fix default sort ordering

Change the default sort order of package_search() to 'relevance asc,
metadata_modified desc'. We want to sort by relevance by default, but
when there's no search query relevance is meaningless, in that case fall
back on showing the most recently modified datasets first. Also changes
the sort ordering of the "Relevance" option in the "Order by:" dropdown
to 'relevance asc, metadata_modified desc' instead of just 'relevance
asc'.

The previous default ordering was 'score desc, name asc'. I'm not even
sure if that works, it seems to disagree with the sort strings that the
dropdown gives you, when you chose relevance from the dropdown you got
'relevance asc' not 'score desc' (and the datasets appeared in a
different order then the default), and when you chose name you get
'title_string' not name.

Previously we've fallen back on showing datasets alphabetically but
that's boring as it simply means that all the datasets beginning with 'a'
are always shown. Last modified seems more interesting and changes over
time. Popularity is not an option because that only works if the page
view tracking feature is enabled.

Move the logic that selects the default sort order for package_search()
out of lib and into package_search().

The package_search() action function now returns the sort order it used
in the 'sort' key of the returned dict, and the package controller sends
this to the templates to decide which sort ordering to show selected in
the "Order by:" dropdown. Previously the package controller and action
function each had their own logic and the dropdown was out of sync with
the actual sort order.

Fixes #714.
[#541] Add docs for highlighting popular datasets and resources

Also mention that tracking summary data is also available for resources
via the API, not just packages.
[#541] Document how to show dataset and resource view counts in templates
[#541] Document showing most popular datasets on front page
[#541] Reference Google Analytics extension in Tracking docs
[#730] Add tracking_raw_table to model

The tracking_raw table was being created by a migration script, but was
not actually defined anywhere in ckan's model. This means that in tests,
ckan.model.rebuild_db() would not clear the tracking_raw table, and the
old data would then leak it into tracking_summary as well. Adding
tracking_raw to the model makes rebuild_db() behave as expected again.
[#730] Make sure 'sort' is always in package_search's data_dict

If data_dict contained no 'sort', the default value was not being added
if the data_dict did contain 'abort_search': True. The code nonetheless
tries to access data_dict['sort'] later on and crashes. (Isn't this what
schemas and validation are supposed to be for?) This was causing a test
to fail. Adding the default 'sort' value to data_dict even if
'abort_search': True is there fixes it.
[#714] Fix some solr package search tests

CKAN used to convert 'sort': 'rank' into 'sort': 'score desc, namae asc'
but since commit ca04063ce061fb80375e73d5aad865ebd6e0ae6d ([#714] Fix
default sort ordering) it no longer does this, which breaks these tests.
Update the tests to pass 'score desc, name asc' directly instead.
[#714] Use score not relevance in default sort order

'relevance' is not actually in the solr schema so it doesn't do
anything, score is the one we want.
[#714] Fix pagination tests

Change create_arbitrary() to always create datasets in the same order,
instead of a different order each time. Update pagination tests to
expect datasets in the new default sort order.
[#714] Fix an intermittently failing test

This test depends on the order of the two datasets. The default sort
order has changed now to most-recently-modified-first when there's no
search query, and since the test creates the two datasets in a random
order the search returns the datasets in a different order each time the
test is run, giving a 50/50 chance that the test will fail.

Change the test to not depend on the fixed order of the datasets.
[#541] Tweak page view tracking docs

Just clarify the docs a bit, and also mention that "recent" means last
14 days and that paster export is for datasets only.
[#541] Small tweak to page view tracking docs
Change demo.featured_groups name and add docs (Fixes #584)
[584] Specify that group names or ids are alllowed