Merge pull request #710 from haiwen/fix-win-strftime

fixed strftime on win32 server, Closes haiwen/seafile-client#134
[server] rename httpserver to fileserver

The name "httpserver" is misleading, since it only handles raw file
upload/download.
Merge pull request #715 from haiwen/fserver

[server] rename httpserver to fileserver
[server] Add cache support for repo

  - [fix] correct some typos and mistakes mentioned by killing
  - [fix] expire cache in seaf_branch_manager_test_and_update_branch in branch.c
  - [fix] expire cache in set_virtual_repo_base_commit_path in virtual-repo.c
  - [impl] TTL support for cache