Update HelperFunctions.cs

Optimization to AddImage

* minimize closure allocations by replacing LINQ with foreach when needed
* use lookups when possible
* reuse filtered items, pre-compute when possible
* use lighter Monitor for isolated storage locking instead of Mutex
* fix DocX references to be real project references instead of DLL references

Add method to insert chart after paragraph

On my search to solve the inserting problem of tables and paragraphs I change this code.
If the document.paragraphLookup is always correct or filled no problem.
But why depend on document.paragraphLookup if it can be done direct?
So this is not a bug.
For me it is not clear why we have the dictionary paragraphLookup.
Is there a real need for the dictionary paragraphLookup, or is it just a result of historical starting ideas and should it be cleaned?

Update Container.cs

The paragraph startindex and endindex are corrupted in Document.paragraphs[].
The result was a wrong insertion of paragraphs and tables. (at wrong locations)
The function GetParagraphs had the bug. the variable index in that function should be updated after creation of the paragraph not before

The function public virtual List<int> FindAll(string str, RegexOptions options) was only resulting one item in the list. instead of a list of find idexes 
If there was only find one no big problem but if it finds more the return index was wrong also .
I think  it is a  typo error, instead of  indexes[0]  it should be indexes[i].

correct width/height setting in Picture class

next newid extended on CreatePicture in Paragraph class
SetWidthsPercentage pwidth calculation extended  with * (96 / 72)  to get pixels from points

Null check added.  Was throwing exception when serializing document o…

Mirror Margins

Mirror Margins boolean attribute

Unit test for script parsing (super- sub- script)

Cleaning up the code

design property: replace try/catch by Enum.IsDefined

Delphin0850 Merge for Headers and Footers margin attribute

issue #63 - fixed FontSize() method in Paragraph.cs to accept half sizes

Added the independent Font implementation

Added unit test Test_Table_SetTableDesignNone() draft. Requires fix in Tables.

Code cleanup - introducing the 'nameof' operator instead of string values

Fixed insertColumns/removeColumns method along with remove. It is now able to work with merged cells.

Added a method to delete cells

Added gridSpan property to cells

Added gridAfter property to rows

Able to add columns to tables where each row have different amount of
cells

Allowing InsertColumn method take into account merged cells for multiple
row add columns where the count of cells is less than the index but is
not less table column count