Support --hide-kernel-threads option for web interface

This adds support for the `--hide-kernel-threads` option in web mode.

I tried also enabling the `--tree` option for the web UI, with:

    diff --git a/glances/core/glances_webserver.py b/glances/core/glances_webserver.py
    index f83793a..4a9e63b 100644
    --- a/glances/core/glances_webserver.py
    +++ b/glances/core/glances_webserver.py
    @@ -38,6 +38,10 @@ class GlancesWebServer(object):
                 # Ignore kernel threads in process list
                 glances_processes.disable_kernel_threads()
     
    +        if args.process_tree:
    +            # Enable process tree view
    +            glances_processes.enable_tree()
    +
             # Initial system informations update
             self.stats.update()
     
However the process list is built using a table, so each tree level on the right becomes as large as the biggest one, which is ugly even when aligning on the left.

I don't know if there is a way to fix this without rewriting the template to not use a table, so I am giving up the tree view in web mode for now.