Refactor global static variables and move hash to shared object

[daboehme]

Better encapsulates the global static variables in Adiak. Also moves the hash list to the shared object, and uses hash to look up entries by name in the adiak_get_nameval* functions. Fixes #40.

[baallan]

Thanks for looking into #40.
@daboehme it's a couple of nits, but:

• it would be nice if strhash here were named strhash_djb2 since that's what it is algorithmically.
• it would be nice if it was declared as size_t or uint64_t instead of unsigned long; probably size_t. We still have architectures where long is 32 and long long is 64 bit.

[daboehme]

Thanks @baallan - I addressed these in #42 now.