Add features from N98 layout helper

[sreichel]

See #321, #336 (netz98/N98_LayoutHelper#10)
Ref #416

N98_LayoutHelper is one of the modules that i have used everywhere ... most important function are already in LTS core code (remove links, improved breadcrumbs), only one usefull change at Page_Head is left ...

This PR adds two args to Mage_Page_Block_Html_Head::addItem() mehtod ...

     * @param string $referenceName name of the item to insert the element before. If name is not found, insert at the end, * has special meaning (before all / before all)
     * @param bool $before If true insert before the $referenceName instead of after

(todo ... change composer.json to prevent install of N98 module, add documentation)

[rjocoleman]

@sreichel do you want a hand with this?

I can add:

• replace in composer.json:

{
  "replace": {
    "n98/n98_layouthelper": "*"
  }
}

• Some docs, as this feature is super useful but quite hard to understand, so docs are important - where should they go?

[github-actions]

Unit Test Results

1 files  ±0  1 suites  ±0   0s ⏱️ ±0s
0 tests ±0  0 ✔️ ±0  0 💤 ±0  0 ❌ ±0 
2 runs  ±0  2 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 57563fc. ± Comparison against base commit 89a7f2b.