Improve treatment of exceptions raised by bigbluebutton-api-ruby

[mconf-daileon]

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Author Name: Leonardo Daronco (Leonardo Daronco)
Original Redmine Issue: 1949, http://dev.mconf.org/redmine/issues/1949

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Several places in the gem where bigbluebutton-api-ruby is used, there's a "begin rescue" block to prevent raising exceptions in case of API failures.
This is good, since we want to treat the exceptions instead of raising them to the user, but at the same time most of these "begin rescue" are hiding the real exception, even for administrators. We should review all places where exceptions are caught and, at least, print the exception to the log files.

Also, API calls that result in errors (checksum errors, for instance) should not get to the user as a "checksum error", but as a more generic "API error", while still being logged as the full error.