Module dependencies: Removing external module dependencies

[NEllis280]

Pull Request (PR) description

This PR removes the xSCCMSql resource in favor of using SQL DSC. Also, this PR removes portions of the xSCCMPreReqs resource in favor of using NetworkingDSC. The PrimaryInstall example has updated examples of SQL installation and firewall configuration.

Task list

• [x] Added an entry to the change log under the Unreleased section of the file CHANGELOG.md. Entry should say what was changed and how that affects users (if applicable), and reference the issue being resolved (if applicable).
• [x] Resource documentation added/updated in README.md.
• [x] Resource parameter descriptions added/updated in README.md, schema.mof and comment-based help.
• [ ] Comment-based help added/updated.
• [ ] Localization strings added/updated in all localization files as appropriate.
• [x] Examples appropriately added/updated.
• [ ] Unit tests added/updated. See DSC Community Testing Guidelines.
• [ ] Integration tests added/updated (where possible). See DSC Community Testing Guidelines.
• [x] New/changed code adheres to DSC Community Style Guidelines.

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This change is 

[codecov[bot]]

Codecov Report

Merging #102 (ac9eebb) into master (250092b) will increase coverage by 0%. The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #102   +/-   ##
=====================================
  Coverage      98%    98%           
=====================================
  Files          60     59    -1     
  Lines        8583   8547   -36     
=====================================
  Hits         8448   8448           
+ Misses        135     99   -36