even more autoconf changes!

removals:
    .travis.yml - no more.
    INSTALL - replaced by INSTALLATION section in README

Makefile:
    allow custom defenition of prefix from ./configure via prefix.txt
    addition of debug target, turns on CC, CFLAGS, and DEBUG macros in main.c
    addition of install-strip target
    install and uninstall targets now follow
    ENDL->NEWL
    addition of distclean target - removes all ./configure-generated files

README:
    addition of INSTALLATION section
    updated to reflect new 'make install' target

configure.ac:
    all AC_CHECK_* (excluding AC_CHECK_TOOL) now report an error on failure
    now checks getopt.h
    now allows to specify prefix, which is copied to prefix.txt

{main,btcapi,cmdlineutils}.c:
    now includes ./configure-generated config.h for preprocessor checks

main.c:
    addition of -v option - version

cmdlineutils.c:
    addition of void version(char *prog_name, char *version) function - prints version