Swift Package Manager Support for v. 1.X

[eduardoperez-nbcuni]

Description

This PR implements Swift Package Manager support for the version 1.X.

Change Notes

• Added new class Package.swift to implement the Swift Package manifest.
• Since SPM doesn't support Objective-C/Swift code on the same target, a new internal target for all the Obj-C classes was created in the Package manifest: HLSObjectiveC.
• Target mamba is the only target exposed to be implemented. [Please note that HLSObjectiveC target is an internal target for Swift Package Manager support, which is not open to the implementors.]

• There was a small re-structure in the folders containing Obj-C classes:

1. Now they are contained in the mambaSharedFramework/HLS ObjectiveC folder.
2. Folder HLS ObjectiveC contains an include folder for the publicly exposed headers.
3. Mamba.xcodeproj was modified to reflect the new folder structure.
4. mamba.podspec was modified to exclude SPM support files.

• New class Exports.swift was created. This class exposes Objective-C public headers for Swift use. More information about this in here. In the section EXPOSING YOUR OBJC TO SWIFT USERS
• Due the "folder structure" nature of SPM, some imports were added to reflect SWIFT_PACKAGE usage.

What is different from previous PR?

• This new PR points to develop_1.X, instead of release version 1.5.0.
• No more Symlinks. Now the public headers are present in the include folder.
• Exports.swift and Package.swift are inside the Mamba.xcodeproj for ease of access. (But please note that in order to build and compile the Swift package, opening the file Package.swift is required. Mamba.xcodeproj cannot build/compile the Swift Package).
• Instead of multiple internal headers, only two were required this time:

1. HLSObjectiveC - Target for ObjC code. [This is needed because we can't mix languages in SPM].
2. HLSParserError. [This is needed because HLSParserError shares error codes to both ObjC and Swift classes, therefore, in order to make it available for Swift and ObjC targets, it needed to be extracted from both to have its own target.]
3. Added Copyright notices in new classes. (Exports.swift and Package.swift)

Testing Sample Apps
In order to test these changes, I have created these sample apps that implements mamba as:

1. Carthage - MyMambaAppCarthage folder
2. Cocoapods - MyMambaAppCocoapods
3. SPM - MyMambaAppSwiftPackageManager

MambaSamples-develop_1.x.zip

Pre-submission Checklist

• I ran the unit tests locally before checking in.
• I made sure there were no compiler warnings before checking in.
• I have written useful documentation for all public code.
• I have written unit tests for this new feature.

[dcoufal]

Thanks so much for the PR! Looks great to me.