Allow multiple resources with same name tag

[roni-frantchi]

On our setup, we have several Subnets and Security Groups associated with our VPC.

The motivation is instead of having name our subnets differently and having to specify each of name in serverless.yml, we add a common label to them all such as private_rds to all of them, allowing our plugin setup to look like this:

custom:
  vpc:
    vpcName: 'whatever'
    subnetNames:
      - 'private_rds'
    securityGroupNames:
      - 'private_rds'

This will match all subnets\security groups who share that name.

To achieve that, the assertion that the plugin makes that the number of parameters must match exactly the number of subnets found for them must be changed to allow less parameters than resources found.
In less resources than parameters are found, the plugin will fail as it used to.

[roni-frantchi]

Moved to #18 so we can merge from env0:multiple-resources-same-tag instead of env0:master