add docs for ngx_http_sysguard_module

Chinese and English version.

Signed-off-by: Paul Yang(InfoHunter) <paulyang.inf@gmail.com>
add docs for ngx_http_upstream_dynamic_module

English and Chinese versions.

Signed-off-by: Paul Yang(InfoHunter) <paulyang.inf@gmail.com>
fix grammar error in docs

Signed-off-by: Paul Yang(InfoHunter) <paulyang.inf@gmail.com>
Fix doc errors for sysguard and upstream_dynamic

Signed-off-by: Paul Yang(InfoHunter) <paulyang.inf@gmail.com>
Merge pull request #508 from InfoHunter/master

add docs for sysguard module and upstream_dynamic module