EZP-21324: Fixed missing references to copied image attributes

- eZImageType::postStore() adds references from ezimage attributes
- An update script (update/common/5.3/restoreimageslinks.php will add missing
  relations for existing data

Also changed removeAlias code. Should now check correctly:
- only remove ezimagealias entries when they're not used anymore
  (handles duplicates if any)
- only removed files when not used anymore.

This means that we accept that when a copy of a content with an
image is made, we accept that archived versions in the copy will
reference the same file than archive versions in the copy source.

EZP-21324: changed removeAlias() prototype

Doesn't accept an eZContentObjectAttribute argument anymore.
The method is always invoked on the instance it must be modified.

EZP-21324: Fixed postgres error

fetchListByFilePath now uses asObject=false, since it doesn't
really make sense to return incomplete objects (due to the duplicates
inserted in ezimagefile)

Fixed removeAllAliases()

We just don't use it anymore. removeAliases() does the job.
The only difference is that removeAliases() will set the
attribute's XML to an empty value, while removeAllAliases()
won't, meaning that the change will create a light overhead
on the database.

EZP-21324: Prevented duplicates in ezimagefile

`eZImageType::postStore()` won't add duplicates to ezimagefile anymore.
EZP-21324: Tests

Added test scenario for content removal

testRemoveCopy also checks that the deleted attributes are no
longer referenced by any ezimagefile record

Added test case to removeCopy

Now tests that all alias files are effectively removed from ezimagefile.

Tests the case where the published version of an image
has more aliases than the archived versions: during copy(),
references to those aliases are created by eZImageType::postStore(),
but are copied to new references instead of being removed,
since the attribute is not the image owner.

These ezimagefile entries are orphan ones, and aren't removed
when the object is deleted.