formio: Portal UX improvements to replace the "Submit a Form" button with a grid

[bobslee]

In the Portal, the "Submit a Form" button was just a quick and simple way to provide accessible Forms.
Consider and design a new (grid) layout.

Otherwise implement new form builder setting (field), to allow form under the "Submit a Form" button.

Related issue: #52

REQUIREMENTS

1. Expand/collapse Forms listing

A button which expand/collapse the listing of Forms to choose.
Also consider whether we need a new kind of nav/menu under /my/formio.

2. Form items layout

Preferable a horizontal/grid layout (eg. tiles).
Would be nice to show an icon with title for every tile (item). The icon/image will be optional to upload in the formio.builder.

3. Obtain the formio.builder characteristics

The grid layout (forms listing) needs to obtain and show some formio.builder characteristics, for example:

Some characteristics:

• Field sequence: to order the formio.builder in the grid
• (New) field category_id = Many2one("formio.builder.category"): to group the formio.builder items per Resource Model (group, heading)