Merge from origin master

Updated copyrights to say 2018 (instead of 2016).

Updated copyrights to 2018 (from 2016). Also edited `about.py` so the year is automatically updated.

CONTRIBUTING.md: Be more explicit about logfile paths

Present full path to necessary logfiles under both Windows and UNIX-like systems.

More detailed export dialog progress, including estimate time remaining, FPS, and more accurate percentage. Thanks Peter!

Add preset xml file for chromebook target

Log length of metrics response, not (non-ascii) contents

Icon/pointer fixes

Track file-import path, the same way export path is tracked (issue #96)

Use source path for images, not destination

The response to the Google Analytics HTTP request is apparently a GIF
image, which was being dumped to the logfile and console output as raw
bytes, corrupting the output. Instead we just log the length of the
response content, in bytes.

Adding new developer page to documentation, with step by step instructions on getting a Ubuntu development environment setup for libopenshot, libopenshot-audio, and openshot-qt.

Split Clip dialog now sends focus back to slider after clicking 'Start' or 'End'  or 'Play' (to make it easier for frame-by-frame arrow keys)

Change the if statement for default language to use system default

Enable text wrapping in table cells (addresses #1262)