* Update arch-common.sh

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* introducing saf_wrapper - a transparent API to use the file descriptor via custom AVIO for saf: Url

* demonstrate how use to use SAF with some demo tabs

SAF is enabled for API 19 or higher
SAF pickers are used for FFprobe on CommandTabFragment and for video output on PipeTabFragment

* Revert "demonstrate how use to use SAF with some demo tabs"

This reverts commit 97b2581

* add SAF tab with two buttons

* change the getSafParameter handles filenames with spaces

see alexcohn#1 (comment)

* take advantage of Cursor being Closeable

* provide NBSP in hexa, to make sure that git and editor don't destroy it

* Avoid "rw" because it may not be supported (e.g. Google Drive).

Also, some code cleanup in SafTabFragment.

* don't run FFprobe after video playback

* ACTION_GET_CONTENT is better than ACTION_OPEN_DOCUMENT: it gives us more options to choose.

* add closeParcelFileDescriptor to fix working with Google Drive

keep the temp files open, we must keep the ParcelFileDecriptor until the fd is closed

attempted to close file descriptor XX, expected to be unowned, actually owned by ParcelFileDescriptor XXX

fixing #634