Edit gen-ext-timezones.py file to generate new fractional timezones

:Release Notes:
gen-ext-timezones.py should now generate all fake Etc timezones from -14,
-13:30,...0,... -11:30, 12.

:Detailed Notes:
In order to support ability for the system to have manual timezones with
a granularity of 30 min timezones, the ext-timezones.json file should now
include all the timezones from -14 to +12 , thereby adding 26 new timezones.
This change modifies the gen-text-timezones.py script to add these new
fractional timezones.

:Testing performed:
Verified that the ext-timezones.json file now has 54 entries under "syszones".

:Issues Addressed:
[BHV-8473] Add fractional Etc timezones

Open-webOS-DCO-1.0-Signed-off-by: Sapna Todwal <sapna.todwal@lge.com>

Change-Id: If362c631195cb5786c84ceb1852a71ae71310f58
Reviewed-on: https://g2g.palm.com/5741
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Tested-by: Keith Derrick <keith.derrick@lge.com>
Merge branch 'develop'