Better container support for linux web apps

[mcdafydd]

- Variable descriptions clarify valid container and non-container values for `fx` 
- Setting the `fx` variable to `compose` or `kube` triggers base64 encode of `fx_version` variable
- Set default value for storage_accounts variable 
- Add ip_restrictions support in site_config

[tw1984]

In terms of IP restrictions, I find it helpful if it's clear in the description whether it's an 'allow' or a 'not allowed.'

description = "A list of IP addresses in CIDR format specifying Access Restrictions." Is this an allow or a block?

[mcdafydd]

Thanks for the feedback. I added a test for ip_restriction and clarified its behavior in the variable description.

It looks like there's been an issue open for quite a while to update support for this feature to the latest with support for allow/deny, priority, etc.

hashicorp/terraform-provider-azurerm#2488
hashicorp/terraform-provider-azurerm#4383 (comment)