[DEV-1377] Change version of mustache in REQUIREMENTS to 0.5.3.
[DEV-1377] Alter mustache required version to >=0.5.0.
[DEV-1377] Alter settings rendering to use latest pystache version.
[DEV-1377] Remove old-pystache SettingsTemplate.
[DEV-1377] [DEV-1377] Update requirements to reflect new pystache version.
[DEV-1320] Merge branch 'DEV-1377' into DEV-1320: update pystache dependency.