bump version number to 1.5 (3).
Merge branch 'release/1.5'
Merge tag 'release-1.5' into dev

Features added:

 * Conceive file mapping schema (#21)
 * Directory Listing (#22 #23)
 * Mount Notification (#26)
 * Unmounting logic (#44)
 * File Reading (#48)
 * MIME detection (#49)

Bugs fixed:

 * USB Drive would not show up in SAF (#24)
 * All zero return value (#38)
 * Date was falsely shown as 1st Jan 1970 (#47)
 * Crash when browsing Sub-Dir (#61)