Updates to data collection and synchronization

This PR makes data collection more robust and fixes some bugs in syncdata.sh

README.md

• Changed "Dependencies" section to "Installing"; added more detailed installation instructions

datacollectiongui.py

• Bugfix: nonexistent attribute references in DuploCorpus were changed to reference definitions.py
• Disabled IMU battery status check

duplocorpus.py

• Bugfix: fixed empty metadata array check

metaweardevice.py

• Deleted unused MetawearDevice methods related to logging
• Changed default bluetooth interface to pygatt
• MetawearDevice.init_streaming() now uses pymetawear API instead of mbientlab's lower-level python wrapper

primesense_datastream.py

• skimage now used in place of OpenCV

syncdata.sh

• Bugfix: echo prepended to several lines made the script operate as if in dry run mode
• Bugfix: rsync was being run with -n (dry run again)
• New sync method: first check if local and remote metadata files differ. If so, replace remote metadata file with local metadata file and upload any new local files to remote server