Don't set AT_SPI_CLIENT

This is not necessary anymore with latest at-spi2-atk
(See commit 683739dea15d7c02c217a404d8c5d9d7af076a57)
Commit from Sugar Labs: Translation System by user cjl.: 40 of 40 messages translated (0 fuzzy).
Commit from Sugar Labs: Translation System by user cjl.: 40 of 40 messages translated (0 fuzzy).
Allow override of user library path

This allows for override of ~/Library the same way that can be done
for ~/Activities. Useful for automated testing.
Commit from Sugar Labs: Translation System by user cjl.: 40 of 40 messages translated (0 fuzzy).
Fix pep8 errors

pep8 1.6.4 detects more issues
Avoid use of uuid module

Upon import of uuid, that module uses ctypes.util to find libuuid/libc,
which involves forking a shell process which then forks and runs ldconfig.

ldconfig performs a whole bunch of disk accesses. This is a slowdown.

uuid.getnode() is also documented to be slow. Lets avoid using it in
the activity launch path; we don't need such a high degree of
randomness.

This makes activities launch 1-2 seconds faster on XO-1.
Merge branch 'at' of https://github.com/dnarvaez/sugar-toolkit-gtk3 into dnarvaez-at
Pass activity name to the webactivity
Fix pep8
ContentBundle cleanups

Share get_installation_time() between all bundle types so that it works
with content bundles.

Add get_tags() stub, this is called by Sugar.

Remove unused fields: l10n, category, subcategory, etc.

We remove support for running OLPC's content bundle indexer.
This is assumed to go away now that Sugar will support content bundles
as first-class objects.

Some minor behavioural fixes and cleanups.

This now implements http://wiki.sugarlabs.org/go/Content_bundles
and when care is taken to include all the fields required by old
Sugar versions, there is no change in compatibility of existing or
new content bundles.

Required for http://wiki.sugarlabs.org/go/Features/Content_support
Icon: handle image loading errors

If the icon can't be found, fall back on showing a generic icon.

Useful when activity/content bundles specify a bad icon, which is
unfortunately true for most content bundles in current existance
(because the icon field was previously unused).