(Bug 1867) Add reading filter module to core2

* adds in a SubscriptionFilter class to S2
* adds in a built-in function to S2, journal_subscription_filters, returning a list of
  SubscriptionFilters
* adds in appropriate module variables in core2
* adds a "print_module_readfilters()" S2 function to print the module; it uses the standard
  module list printing
* adds "property use module_readfilters_group;" to all propgroup modules sections in layouts

Things to double check:

* Test that private filters do not show to people other than the journal owner; I've tested this but
  it's very critical.
(Bug1867) Fix readfilters module ordering

Fix the readfilters module ordering for Blanket and EasyRead.
(Bug 1867) Review code clean up

This patch:

* Standardizes the module name around subscription filter; that's what they're called
  in other areas of the site, so we should be consistent.
* Standardized the SubscriptionFilter class to be consistent in naming; it now has
  a string url var instead of a string link, because the Link class seemed overkill
* Abstracts away the id of the Subscription filter; we can add it in if we need it later
* Improves the logic of adding a filter to the list of filters displayed
(Bug 1867) Add a manage link to the filter module

Implements the same way other management links have been implemented.
(Bug1867) Improve filter module print checks

Now the module checks to see if it should print:

* It shouldn't print for communities or for syncdication journals
* It shouldn't print if there are no filters for it to print
(Bug1867) Filter module shouldn't show for comms

Makes it so the filter module doesn't show up in the
theme customization wizard for communities, as they
cannot use it.
(bug 4655) Add CONTRIBUTING.md

first stab at a CONTRIBUTING.md, mostly just references to other places
info can be found.
Merge pull request #295 from rahaeli/bug-4655

(bug 4655) Add CONTRIBUTING.md
(bug 4908) change target for redirect to .bml-less version

also, while i'm at it, correct a grammatical error in one of the text
strings!
(bug 4897) UNTESTED: add hook for dreamwidth.org specific text

the hook itself is in the dw-nonfree patch forthcoming. THIS IS NOT
TESTED, since my 'hack isn't set up to do payments, so it may not work
or the formatting may be weird!
(Bug 4680) Add the word "settings" beside the gear
Merge pull request #298 from afuna/settings-gear-bug4680

(Bug 4680) Add the word "settings" beside the gear
Bug 4748 - Bases: new themes
http://bugs.dwscoalition.org/show_bug.cgi?id=4748
-- 4 new themes by rising
Bug 3472 - "Back to Top" title link should be included in all Dreamwidth styles by default
-- Add 'back to top link' to Bases styles
-- All credit goes to @miketrethewey
Bug 4240 - Profile module: match text links with icon links
http://bugs.dwscoalition.org/show_bug.cgi?id=4240
-- Use text strings from en.dat instead of Core2 props
-- Rephrase some strings
-- Remove no obsolete props from Core2
-- All credit goes to @jeshyr
Merge pull request #299 from ninetyd/bug4748/bases_themes

Bug 4748 - Bases: new themes
Merge pull request #300 from ninetyd/bug3472/bases_backtotop

Bug 3472 - "Back to Top" title link should be included in all Dreamwidth...
Bug 4845 - subscribing to a comm gives incorrect text on the confirmation screen
http://bugs.dwscoalition.org/show_bug.cgi?id=4845
-- Don't add extra text for communities
(bug 4908) correct changed string

Oops.
Merge pull request #296 from rahaeli/bug-4908

(bug 4908) change target for redirect to .bml-less version