Tweaks + add new icons

[hadim]

Here are a few tweaks that I needed for myself. Feel free to take what you want:

• Add icons for birth, twitter and google scholar
• Ability to add an href for a resume entry title
• Color location in resume entry
• Add spacing aboe heading level 1
• Address in italic and remove bold

[hadim]

See https://github.com/DeveloperPaul123/modern-cv/issues/45 for some context

[DeveloperPaul123]

Thanks for the PR! Overall this looks quite good with a couple of exceptions:

• The extra spacing above headers
• Italics for the address

I have reverted these changes, but everything else looks good. Thanks for the contribution.