[BRANCHES] Giving some sanity to dates

[Guillaume Emont <guijemont igalia com>]

Hi all.

Here is a refreshed (rebased against latest master and updated
accordingly) of my branches to change the way we handle dates in Grilo.

The two big changes introduced here are:
 - There are new keys replacing the old GRL_METADATA_KEY_DATE. The new
keys are more precise in meaning, and more could be added in the future
if needed.
 - These keys are of the GDateTime type, instead of using a more fragile
c string (in that latter case, the parsing of that string into something
more usable would happen at the last moment, when it's too late to
report a "bad date" error)

Plugins have been updated according to this scheme.

I don't feel like spamming the mailing list with plenty of patches
again, so I'm just giving references to the branches here:

 * Grilo
  repos: git://gitorious.org/~guijemont/grilo/guijemont-sandbox.git
  branch: date_fixes
  web:
https://www.gitorious.org/~guijemont/grilo/guijemont-sandbox/commits/date_fixes
 * Grilo plugins
  repos:
git://gitorious.org/~guijemont/grilo/guijemont-grlplugins-sandbox.git
  branch: date_fixes
  web:
https://www.gitorious.org/~guijemont/grilo/guijemont-grlplugins-sandbox/commits/date_fixes

Can someone please review that before it needs loads of changes to
follow the evolution of master again?

Please note that these are candidates to merge in master and _not_ in
0.1.x, since the changes break the API.

Feel free to ask any question about it.

Cheers,

Guij