Add application form fixes

Fixes for:
https://github.com/opentechinstitute/luci-commotion-apps/issues/19
https://github.com/opentechinstitute/luci-commotion-apps/issues/18
https://github.com/opentechinstitute/luci-commotion-apps/issues/20

This makes apps permanent by default, and restricts text input fields to 254 max characters. To test:

1. Flash node and make it a gateway
2. Try to input more than 254 chars in any text field (should not work)
3. Try to input a port > 5 chars and a ttl > 2 chars (should not work)
4. Add an app with a description and name and icon URL of 254 chars, port = 80, and URL/ipaddr = http://google.com/12345678901234567890... (fill up max 254 chars). This should succeed.
5. Now edit this app, and uncheck the permanent box. Save the app.
6. Edit the app again, and the permanent checkbox should be unchecked.

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