Fixed a number of spelling errors; removed rhoInv

Fixed a number of spelling errors in names of functions and variables:
ellement_size --> element_size (found 10 times)
get_elepasedTime --> get_elapsedTime (found 4 times)
OPENCL_PORGRAMM_PATH --> OPENCL_PROGRAM_PATH (found 2 times)
infrmation --> information
chouse --> chosen
appropriet --> appropriate
instaled --> installed

Completely removed data block rhoInv which was necessary only for basic
SPH

Some other minor changes