level: in CRF/CQP encodes, allow user specifed level to increase stream level

See the comment
common: introduce x265_slurp_file, reads data from file to string buffer.
param: add more param options to print as string
param: use dashes consistently in param2string
rc: store final cu counts in frameStats as a percentage of total # cus

there exists a mismatch in the total no. of 16x16 blocks calculated between encoder and RC.
rate control counts no. of 16x16 blocks without considering the border extension of source pic.
keeping cu stats as percentage avoid this problem when used later in RC's 2nd pass.
param: keep the total frame count of the input video in param.

to be used in 2 pass. In case this is not available, the value can remain as 0.
rc: init RC data for second pass in a multi pass encode
frameencoder: store reflagrows as a member variable
cmake: nit - about target arch strings
rc: nits
param: fix typo in d1d5b377294e