simplify vdb.
1. line number information has been removed for simplicty
2. remove all macros/overloaded functions from header, use simple C functions
3. mark functions "weak" rather than static inline to make sure they appear in executable, but can still be included twice
4. begin and end are now sent to the server, this helps resolve flickering issues
fix label display bugs
make header file C compatible
remove dead fn
linux compile issues
make windows friendly. update docs
Merge branch 'develop' of github.com:zdevito/vdb into develop
update links in README