feat: atclient pkam_authenticate

[JeremyTubongbanua]

related to #39

- What I did

general changes:

• use #ifdef X_H, #define X_H, #endif as opposed to #pragma once to ensure compatibility with different compilers
• utilize unsigned long as opposed to size_t to ensure compatibility with different compilers
• run_ctest.sh in atclient and atchops to run ctests

atchops:

• new aes.h and aes.c -> contains generic aes key generation and aes bits (128 and 256) enum
• new iv.h and iv.c -> contains generation of base64 and non-base64 initialization vectors
• new rsakey.h -> out sourced the rsakey interactions from the rsa lib
• refactored tests to print things more tidely

atclient:

• new atclient_pkam_authenticate function:

int atclient_pkam_authenticate(atclient_ctx *ctx, atclient_atkeys atkeys, const char *atsign);

• new atkey.h and atkey.c -> represents an AtKey in the atProtocol
• new atkeys.h and atkeys.c -> holds decrypted RSA and AES keys in base64 and atchops keys to be used in subsequent cryptography
• new atkeysfile.h and atkeys.c -> represents the atkeys file (holds encrypted cryptographic keys and base64) as well as file reading functionality
• new atlogger.h and atlogger.c -> logging utility
• new atstr.h and atstr.c -> represents the 3 dimensions of a string: buffer length, buffer pointer, and the written length. to be used inside of structs
• new metadata.h and metadata.c -> represents metadata in the atProtocol

examples:

• examples refactoring - upload placeholders for include folders and static libraries and not the actual files
• new atkey example
• new pkam_authenticate example
• new reading_atkeys example

- How I did it

with my bare hands

- How to verify it

tests (even though refactored) are passing

- Description for the changelog

[realvarx]

LGTM

[JeremyTubongbanua]

@realvarx introduced #46