Add new functions required from the DM plugin
Add new functions required from the DM plugin

There are 5 functions that blivet uses from the pyblock and which can be
implemented in the DM plugin instead allowing blivet dropping its dependency on
pyblock.

Also fix some functions' names.

rhinstaller/libblockdev,vpodzime/libblockdev,snbueno/libblockdev,atodorov/libblockdev,atodorov/libblockdev,rhinstaller/libblockdev,vpodzime/libblockdev,snbueno/libblockdev,rhinstaller/libblockdev,dashea/libblockdev,atodorov/libblockdev,dashea/libblockdev,vpodzime/libblockdev