[FIX] ir.translation: translated terms within view definitions were not loaded

The changes for QWeb template translation have introduced
res_id values in PO comments for all `#: view:` terms, as
the real database id needs to be resolved when loading them.

For non-QWeb views this is not necessary and actually caused
the terms to be dropped when the res_id could not be resolved.

Rather than having a different PO comment format for QWeb and
non-QWeb views, we can extend the QWeb hack to force the
res_id to 0 for non-QWeb views.

Fixes issue #1755
[FIX] ir.ui.view: match translated terms without heading/trailing whitespace

As the whitespace is stripped when exporting terms
to translate, it must be done as well when matching
translations at runtime.

Fixes issue #1755 partly
[FIX] web_calendar: make UI string translatable

Fixes issue #1755 partially, when the new term
will be translated
[FIX] account: invoice view - useless trailing spaces in labels