Added makefile for modelsim, reorganized, added components & packages.
- Revised trig_table to use sfixed as output.
- Added DDS to generate I & Q sinusoids from a ufixed value.
- Added mapper to map data values to I & Q symbol amplitudes.
- Added symbolizer to repackage data as symbols.
- Added basic_pkg for simple components.
- Added rf_blocks_pkg for RF blocks (like the DDS).
- Added fixed_pkg for VHDL-2008 fixed-point types.
- Added util_pkg for common library functions and types, used at every level of
  the library.
- Added makefiles to help compile Modelsim libraries.
- Modelsim library "boostdsp" now compiles.
- Modelsim library "boostdsp_tb" now compiles.
Added new symbolizer architecture, added frame_tx component.
- symbolizer_even is like symbolizer, but it only works when each chunk of data
  can be split perfectly into symbols. Generally, everything not using 8-PSK
  will satisfy this requirement.
- frame_tx provides an SRAM-like interface for loading data into a buffer, and
  can turn the entire buffer into a series of symbols. This provides the basic
  functionality needed to have a RF transmitter that other logic can read and
  write to.
- Basic testbenches have been built for symbolizer_even and frame_tx, to
  demonstrate their functionality. They do provide good test coverage, and would
  require some modification to be used for checking many test cases.
Structure set up for comm_systems_pkg, Makefiles made more efficient.
- comm_systems_pkg and associated folders made. This package will hold any basic
  communication system. It will only handle the PHY layer and any hardware-based
  error correction (e. convolutional coding)
- Makefiles for testbench folders weren't checking for changes and were always
  compiling. This has been fixed.
More Makefile fixes, fixed error in trig_table.
Added simple_tx block, showing a simple RF transmitter.