Attempt a more accurate way to get apps for dialyzer PLT building

Assert perl exists before builds (#170)

We had no handling for KERL_INSTALL_HTMLDOCS being set in the shell
properly, as KERL_INSTALL_MANPAGES is handled
There was a typo in the use of KERL_PROMPT in CSH activate scripts

This change implements storing the build configuration in a file which
can later be compared to a potentially new configuration which might
trigger the need to re-run the OTP configuration steps.

We also copy the build configuration into the installation directory so
that at some future time we can write or enhance a command which shows
the build configuration.

Addresses #162 #158

Perl 5 is required to compile Erlang from source. It's used (among other
things) to assemble BEAM opcodes, NIF jump tables and more. We now
assert perl exists on the PATH before we proceed to build Erlang or test
for Perl's version string.

We also now test for Java before we try to find its version. Java is not
required to compile Erlang though, so we don't output any warnings or
errors if its not found.