Fix segfault when calling git_config_get_* functions when a config fails to load

Reinitialize the result code of get_entry() to GIT_ENOTFOUND

Convert gitdir paths to posix on Windows

Apparently, a .git file with "gitdir: path" link on Windows is
allowed to use backslashes in the path.  Who knew?

Fix some documentation issues.

Run Coverity scan on Travis

Update README to include Java, PowerShell bindings

refs: remove the _with_log differentiation

Any well-behaved program should write a descriptive message to the
reflog whenever it updates a reference. Let's make this more prominent
by removing the version without the reflog parameters.

Common

Align `*_dup` functions

Implement @cmn's suggestions for `git_remote_dup`.

This changes git_signature_dup to actually honor oom conditions raised by
the call to git__strdup. It also aligns it with the error code return
pattern used everywhere else.

Add `git_remote_dup`.

Fix a bunch of memory leaks.

Stream packs to the destination

`git_blame_free` already calls `git__free` on `gbr`.