Fixed #1641 - Added cache param in Display layer properties

[MV88]

Added "use cache option" inside Display Tab.
Also saved this prop qhen the map is saved

[coveralls]

Coverage increased (+0.03%) to 78.689% when pulling 6d09428 on MV88:iss_1641_cached_tile into 5359643 on geosolutions-it:master.

[coveralls]

Coverage increased (+0.02%) to 78.684% when pulling ac4f958 on MV88:iss_1641_cached_tile into 5359643 on geosolutions-it:master.

[coveralls]

Coverage increased (+0.03%) to 78.693% when pulling 3260a6a on MV88:iss_1641_cached_tile into 5359643 on geosolutions-it:master.