Fixes #498 - Fix VPC security group limits

[jantman]

Fix multiple issues relating to VPC limits:

• Update the EC2 / Rules per VPC security group limit to support retrieving the current limit value from Service Quotas.
• Remove the EC2/Security groups per VPC limit, which no longer exists.
• Add the new EC2/VPC security groups per Region limit, with value retrieved from Service Quotas

[codecov-io]

Codecov Report

Merging #508 (9aae867) into develop (4a23d3f) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##           develop      #508   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           42        42           
  Lines         3019      3018    -1     
  Branches       452       451    -1     
=========================================
- Hits          3019      3018    -1     

Impacted Files	Coverage Δ
awslimitchecker/services/ec2.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 4a23d3f...9aae867. Read the comment docs.