Use between as temporal operator with QGIS

[arnaud-morvan]

QGIS does not support "During" operator.

[arnaud-morvan]

@sbrunner : it was much simpler than I thought

[sbrunner]

:-)

[arnaud-morvan]

@sbrunner : I need it in 2.2 for ADL and there is big problem with typing (between take two numbers).
As we might restore type checking, here is a new version with new filter operator that accepts strings.

[sbrunner]

I don't think that there is a big problem, but it can be good to have two different pull requests :-)

[arnaud-morvan]

@sbrunner : I've rebase this old PR, still ok for merge ?

[fredj]

looks code but src/ol-ext/format/filter.js needs to be converted to es6 modules / classes

[arnaud-morvan]

Thanks, I forgot to remove this file during rebase, done now.