Script simplifying builds of conan packages

[mm-s]

• Lowered the minimum required version of CMake to build to match the CMake version distributed by Debian/buster (3.14->3.13)
• Simplified the construction of conan packages with an script
• Updated README

Tested in Debian Buster:

scripts/make.sh all

Produces

conan search
Existing package recipes:

benchmark/1.5.0@nemtech/stable
benchmark/1.5.1@nemtech/stable
benchmark/1.5.2@nemtech/stable
boost/1.75.0
cppzmq/4.4.1@nemtech/stable
cppzmq/4.5.0@nemtech/stable
cppzmq/4.6.0@nemtech/stable
cppzmq/4.7.1@nemtech/stable
hello/0.1@demo/testing
libiconv/1.16
milagro/2.0.1@nemtech/stable
milagro/2.0.1-nem@nemtech/stable
mongo-c-driver/1.15.3@nemtech/stable
mongo-c-driver/1.17.0@nemtech/stable
mongo-c-driver/1.17.2@nemtech/stable
mongo-cxx-driver/r3.4.0-nem@nemtech/stable
mongo-cxx-driver/r3.6.0-nem@nemtech/stable
mongo-cxx-driver/r3.6.0@nemtech/stable
mongo-cxx-driver/r3.6.1@nemtech/stable
openssl/1.1.1f@nemtech/stable
openssl/1.1.1g@nemtech/stable
rocksdb/6.6.4-nem@nemtech/stable
rocksdb/6.11.4@nemtech/stable
rocksdb/6.13.3@nemtech/stable
zeromq/4.3.2@nemtech/stable

[segfaultxavi]

The text looks alright 👍

[gimre-xymcity]

rocksdb/6.13.3@nemtech/stable (test package): Calling build()
CMake Error at CMakeLists.txt:1 (cmake_minimum_required):
  CMake 3.14 or higher is required.  You are running version 3.13.5


-- Configuring incomplete, errors occurred!
ERROR: rocksdb/6.13.3@nemtech/stable (test package): Error in build() method, line 13

[mm-s]

I gave up setting cmake min version to 3.13.
This PR is now only about the automation script