Fixed Issue #33 and #34, improved auth support and added better support for pause/resume

This pull request contains five patches.

Patch https://github.com/tuxpoldo/btsyncindicator/commit/35a185930f0c0fbcecdfec170f4c1a6699ffced1 is a direct consequence of https://github.com/tuxpoldo/btsync-deb/issues/12 - if the pause/resume state is persistent across reboots, it's ugly if the indicator shows a connection error when btsync is evidently in paused state. This patch adds real support for pause/resume to the status update routine and session initialisation routine.

Beside of fixing Issue #33 , this patch solves also some additional problems that derive from the fact that username and password were mangled into the URL (beside the security aspect of showing them in logging). It implements authentication using the provided API from the requests library.

The patch https://github.com/tuxpoldo/btsyncindicator/commit/d718631130fd2449e326c2a638319a215cb7d08b adds autologin support to the menu function _"Open Web Interface"_ for installations done with `btsync-user`. Basically this may be a good feature, but power users installing btsyncinidicator manually likely prefer to have full control over authentification. In `btsync-user` the typical user is not aware that the UI is potentially reachable by any user. He installs `btsync-user` and expects a solution as similar as possible to the user experience on Mac/Windows. The automatic generation of credentials will make the system more secure to attacks from concurrently logged in users, but with autologin the user will not see, that his web UI is protected.

The patch https://github.com/tuxpoldo/btsyncindicator/commit/5e0932d1406d943df48eaae50a86b47f71d34cee implements the missing exception handlers for HTTPError exceptions that happen if a transaction does not return 200. Sometime a race condition occurs when resuming btsync and in such a case some requests are done before btsync has fully come up. The result are some 4xx/5xx error codes and invalid data. Without exception handler, btsyncindicator.py terminates itself... Additionally this fixes also Issue #34 

Can you please add also this here. It will improve significantly the pause/resume feature in btsync-user...