[2.3] [Re-build] Manager Theme: Add new logo as inline SVG  + color adjustments to match logo colors

As modx.com has a new logo it seems time to also replace it in the manager. I took the chance to re-use the SVG logo found on modx.com and save us one more manager request as the SVG is embedded inline. To help poor IE8 there is a PNG fallback that only shows up when IE8 is coming (e.g. no additional request for normal users). It scales beautifully BTW =)...(not the PNG though).

ups, @rtrash was faster =), but without the inline SVG change as I see...

Based on issue https://github.com/modxcms/revolution/issues/11776 I tried how it could look with the primary buttons in the new logo colors, happy to hear your comments (and will update PR if not better than before!). I also slightly adjusted the colors $orange, $red and $green to match the logo colors, almost no difference visible actually...

would look like that:
![bildschirmfoto 2014-07-22 um 22 52 04](https://cloud.githubusercontent.com/assets/445501/3665312/b6cad98c-11e4-11e4-9280-6b01328a6e95.png)

![modx managertheme newcolors](https://cloud.githubusercontent.com/assets/445501/3665340/e67675f6-11e4-11e4-83c7-80f845e4b844.gif)


primary buttons
![bildschirmfoto 2014-07-22 um 22 54 00](https://cloud.githubusercontent.com/assets/445501/3665324/c0749dd8-11e4-11e4-9569-25f3e152d4b2.png)

![bildschirmfoto 2014-07-22 um 22 54 25](https://cloud.githubusercontent.com/assets/445501/3665326/c4f4da76-11e4-11e4-8632-f83b6ea5b1a7.png)

window
![bildschirmfoto 2014-07-22 um 22 54 53](https://cloud.githubusercontent.com/assets/445501/3665329/ca930dc2-11e4-11e4-9ddd-ecfbc2787bae.png)