Patch androlog to support report log message timestamps, customised report content & mail subject/attachment name

Patch androlog to support:
* Timestamps in log messages collected for report
* A custom ReportFactory which allows customisation of report contents by adding simple JSON values to a "custom" key
* Custom subclasses of MailReporter which allow email subject & attachment filename to be customised using application or report properties

Report itself considerably refactored to support the "custom" object, & to allow EnhancedReporter impls to get some values from the report for use in mail subject, etc - specifically can get:
* Any key in "device" & "app" objects
* Created timestamp
* Flag indicating whether Report is due to exception or not.
Misc change to ensure the same timestamp is used in all report properties & for filename suffix

Made efforts to ensure that existing extensions will still work:
* Reporter interface unchanged - ReportFactory depends on using an EnhancedReporter, both Reporter impls changed to implement this
* Any subclasses of MailReporter & PostReporter should be ok

Timestamps & ReportFactory class are enabled by config;  by default no timestamps are added & existing report content is used.  Timestamp format is ISO 8601, not customisable yet.

All androlog-it tests pass (once url in PostReporterTest changed as appropriate).
No new tests written for these changes.