Update change log and spec for wrt-plugins-tizen_0.2.76

Update change log and spec for wrt-plugins-tizen_0.2.76

Changed Modules : Power and MediaContent

[Version] 0.2.76
[Project] GT-I8800, Public
[Title] SEL Verification
[Team] WebAPI
[BinType] PDA
[Customer] Open

[Issue#] Jira N_SE-8554
[Problem] Power - Wrong internal brightness value stored when bright lock is requested two times.
[Cause] Wrong internal value saving.
[Solution] Use device_set_brightness_from_settings api instead of saving internal value.

[Issue#] N_SE-8252
[Problem] MediaContent - Don't check offset value. And bug of CAPI function(media_filter_set_offse)
[Cause] N/A
[Solution] Removed offset, count,offset value check code. (now on, check for an error in the CAPI)

[SCMRequest] N/A