vector: adding new vector module for basic operations

  * simple things like adding and/or multiplying vectors together
  * created for simplicity and abstracting from loops
  * eventually will include SIMD operations like with dotprod module
sandbox: adding test of vector operations
vector/norm: adding method to scale by l2-norm
vector: cleaning up and adding new function prototypes in global include
build: adding line about new vector operations to HISTORY
vector: adding certain trig methods
Merge branch 'master' into vector-dev
Merge branch 'master' into vector-dev
Merge branch 'master' into vector-dev
build: updating copyright in vector module
Merge branch 'master' into vector-dev
Merge branch 'master' into vector-dev
Merge branch 'vector-dev' of liquidsdr.org/liquid-dsp
filter: adding fftfilt family of objects

  * efficiently uses FFTs to efficiently realize FIR filter
  * no implementation for fftfilt_rrrf (can be more efficient)
  * needs example (compare fftfilt with firfilt objects)
  * needs testing (autotests)
  * needs benchmark
  * needs additional supporting methods (recreate, group delay, etc.)
  * this has been on my TODO list for ages...
filter/fftfilt: adding example to compare output with firfilt_crcf
filter/fftfilt: adding simple benchmark script
filter/fftfilt: adding autotest script for crcf, cccf types
filter/fftfilt: enabling override to use internal FFT objects
Merge branch 'vector-dev' into fftfilt-dev
filter/fftfilt: using vector type for inner product