Merge pull request #319 from youny626/misc

- \#284 - Change C++ SDK to shared library

- \#260 - C++ SDK README

- \#314 - add Find FAISS in CMake

- \#310 - Add Q&A for 'protocol https not supported or disable in libcurl' issue

## Task

## Software requirements

- Ubuntu 18.04 or higher

- CMake 3.14 or higher

- CMake 3.12 or higher

##### For GPU version, you will also need:

- CUDA 10.0 or higher

- NVIDIA driver 418 or higher

### Step 1 Install dependencies

```shell

$ cd [Milvus sourcecode path]/core

$ cd [Milvus root path]/core

$ ./ubuntu_build_deps.sh

```

### Step 2 Build

```shell

$ cd [Milvus sourcecode path]/core

$ cd [Milvus root path]/core

$ ./build.sh -t Debug

or 

$ ./build.sh -t Release

```

By default, it will build CPU version. To build GPU version, add `-g` option

```

$ ./build.sh -g

```

When the build is completed, all the stuff that you need in order to run Milvus will be installed under `[Milvus root path]/core/milvus`.

## Launch Milvus server

Add `lib/` directory to `LD_LIBRARY_PATH`

```

$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/path/to/milvus/lib

$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:[Milvus root path]/core/milvus/lib

```

Then start Milvus server:

```shell

$ ./stop_server.sh

```

## Troubleshooting

1. If you encounter the following error when compiling: 

`protocol https not supported or disabled in libcurl`.

First, make sure you have `libcurl4-openssl-dev` installed in your system.

Then try reinstall CMake from source with `--system-curl` option:

```

$ ./bootstrap --system-curl 

$ make 

$ sudo make install

```