Fix #9819: Allow access to named tuple's names

Adds a `fieldNames` alias to `std.typecons.Tuple` to return the user-supplied
names.  The actual fields are in an expression tuple, so the
user-supplied names are simply aliases, which previous to this PR, were
not accessible.

https://issues.dlang.org/show_bug.cgi?id=9819

Fix Issue 9819
Remove std.traits.unsigned as scheduled.
Move along some overdue deprecations.
There's no point in scheduling deprecations anymore.

deprecate no longer generates an error, so we might as well just
deprecate directly.
Rename local variables to avoid conflict with local imports
fix property enforcement
Avoid multiple giant h1s in CONTRIBUTING.md
Merge pull request #2263 from 9rnsr/enforceProp

fix property enforcement
Update the Qt signals and slots link.
Merge pull request #2264 from ckakman/patch-1

Update the Qt signals and slots link.
Slight improvement to enforceEx's constraints and its documentation.
Workaround for issue# 12961.
Merge pull request #2260 from jmdavis/deprecated

Move some deprecations along.
Merge pull request #2232 from economicmodeling/fix_9819

Fix 9819: Allow access to named tuple's names.
Merge pull request #2265 from jmdavis/exception

Slight improvement to enforceEx's constraints and its documentation.
Remove deprecated module std.metastrings

This module has been deprecated and scheduled for removal in March 2014.
It is now June 2014.
Merge pull request #2267 from quickfur/del_metastrings

Remove deprecated module std.metastrings
Merge pull request #2262 from 9rnsr/fix_imports

Rename local variables to avoid conflict with local imports
Add missing imports
Merge pull request #2268 from 9rnsr/fix12359

Add missing imports