--exclude-file

Added `--exclude-file` for `emcc` and `--exclude` for `file_packager.py`

Basically it works like `zip`, the patterns provided with `--exclude`  are matched for each file.

Dot files/directories are included by default, and you can specify `--exclude-files .git` or `--exclude-files .*` for `emcc`. Note that you need to escape * in the shell

Fixes #1808

Added a new test case: other.test_exclude_file

Passed all tests that use --embed-file:

test_cube2md5
test_fgetc_unsigned
test_fgets_eol
test_fscanf
test_mmap_file

other.test_ungetc_fscanf
other.test_embed_file
other.test_embed_file_dup
other.test_fs_stream_proto

browser.test_sdl_audio