[tracker] (9 commits) ...Merge branch 'wip/carlosg/gdatetime' into 'master'

[Sam Thursfield <sthursfield src gnome org>]

Summary of changes:

  3028e54... docs: Change lower datetime bound in doc/tests about limits (*)
  74bf9d0... libtracker-data: Change TrackerOntology timestamp to be gin (*)
  dad7a4b... libtracker-common: Add GDateTime helper functions (*)
  006d100... libtracker-data: Update ontology nrl:lastModified with GDat (*)
  57386f7... libtracker-data: Use GDateTime parsing for xsd:date[Time] l (*)
  cc48ba5... libtracker-data: Port datetime SQLite functions to use GDat (*)
  ca80099... libtracker-data: Use GDateTime on update machinery (*)
  e1c060e... tests: Remove old date/time helpers (*)
  63bfb07... Merge branch 'wip/carlosg/gdatetime' into 'master'

(*) This commit already existed in another branch; no separate mail sent