resourceloader: Make timestamp handling more consistent

resourceloader: Make timestamp handling more consistent

* Use time() instead of:
  - wfTimestamp()
  - wfTimestamp( TS_UNIX )
  - wfTimestamp( TS_UNIX, 0 )
  - wfTimestamp( TS_UNIX, time() )
  - intval( wfTimestamp( TS_UNIX, time() ) )

* Consistently use 1 as default instead of 0. Previously the
  unwritten convention was that anything "final" max()'ed with 1,
  and any internal method would use 0, but this wasn't applied
  consistently made it fragile. There doesn't seem to be any
  value in returning 0 only to have it maxed up to 1 (because if
  the 0 would ever make it out alive, we'd be in trouble).

* wfTimestamp returns a string for TS_UNIX. In PHP this doesn't
  matter much. In fact, max() takes number-like integers so
  transparently, it even preserves it:
  > max( 1, 3, '2' );
  < 3
  > max( 1, '3', 2 );
  < "3"
  Just cast it in one place at the very end (StartupModule)
  instead of doing intval( wfTimestamp() ).

* Fix weird documentation claiming getModifiedTime can return
  an array, or mixed.

* Remove 'version > 1 ? version : 1' logic in
  ResourceLoader::makeLoaderRegisterScript. The client doesn't
  have "0 means now" behaviour so this isn't needed. And the method
  was only doing it for variadic argument calls.

Removal of quotes around timestamps reduced the size of the startup
module from 26.8KB to 25.9KB before gzip. After gzip the size was
and still is 5.7KB, though. (From 5456 bytes to 5415 bytes.)

Change-Id: If92ca3e7511e78fa779f2f2701e2ab24db78c8a8