Added 2 new constructors for FileTape which copy the size of existing tape into a new one
Implemented external sort of a Tape using heap sort
Rewritten FileTape constructors implementation to better take advantage of existing constructor calls
Added const to some parameters to indicate their immutability
Added unit tests for external_sort
Slight rewrite of fill_file_with_empty_cells
Adjusted seek offset in some FileTape operations
Unit tests now work with vector of uint32_t as source of test data
Changed file format for a FileTape - added and example in the class comment
Removed prev_line_pos and at_first_line fields from FieldTape
Changed Tape data type from int32_t to uint32_t
Cleand up includes
Implemented FileTape methods
Unit tests are in working state
Disabled warnings as errors
bumped the cmake min version to 3.12 for c++20 support and -j flag
Placed a CMakeLists.txt in each subdirectory of the project