Server certificate trust, code review fixes

Added empty certificate TrustStore that is now used by default
when checking if a certificate is trusted.
Added "Show certificate dialog" developer connection preference
(disabled by default) to use the MemorizingTrustManager instead of
the above TrustStore check.
Fixed typo in comment in SVMPAppRTCClient.

Note: the empty TrustStore, "client_truststore.bks", can be
replaced with one of your choosing. The password to access that
TrustStore should be set accordingly in Constants.java.
Intent filter security, code review fixes

Added check to the battery broadcast receiver in MeasureTask to
check and make sure the received intent has the correct protected
action string.